medicine, the heart valves
by subbia1988
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1. mitral stenosis

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219. VALVULAR HEART DISEASE - Eugene Braunwald

INTRODUCTION

The role of physical examination in the evaluation of patients with valvular disease is also considered in Chap. 209; of electrocardiography (ECG) in Chap. 210; of echocardiography in Chap. 211; and of cardiac catheterization and angiography in Chap. 212.

MITRAL STENOSIS

ETIOLOGY AND PATHOLOGY

Two-thirds of all patients with mitral stenosis (MS) are female. MS and mixed MS and mitral regurgitation (MR) are generally rheumatic in origin; very rarely, MS is congenital. Pure or predominant MS occurs in approximately 40% of all patients with rheumatic heart disease. In other patients with rheumatic heart disease, lesser degrees of MS may accompany MR and aortic valve lesions. With reductions in the incidence of acute rheumatic fever, particularly in temperate climates and developed nations, the incidence of MS is declining. However, it remains a major problem in developing nations, especially in tropical and semitropical climates.

In rheumatic stenosis the valve leaflets are diffusely thickened by fibrous tissue and/or calcific deposits. The mitral commissures fuse, the chordae tendineae fuse and shorten, the valvular cusps become rigid, and these changes, in turn, lead to narrowing at the apex of the funnel-shaped ("fish-mouth") valve. Although the initial insult to the mitral valve is rheumatic, the later changes may be a nonspecific process resulting from trauma to the valve caused by altered flow patterns due to the initial deformity. Calcification of the stenotic mitral valve immobilizes the leaflets and narrows the orifice further. Thrombus formation and arterial embolization may arise from the calcific valve itself, but more frequently arise from the dilated left atrium (LA) in patients with atrial fibrillation (AF).

PATHOPHYSIOLOGY

In normal adults the mitral valve orifice is 4 to 6 cm2. In the presence of significant obstruction, i.e., when the orifice is less than approximately 2 cm2, blood can flow from the LA1 to the left ventricle (LV) only if propelled by an abnormally elevated left atrioventricular pressure gradient (see Fig. 212-2), the hemodynamic hallmark of MS2. When the mitral valve opening is reduced to 1 cm2, often referred to as "critical" MS, a LA pressure of approximately 25 mmHg is required to maintain a normal cardiac output (CO). The elevated pulmonary venous and pulmonary arterial (PA) wedge pressures reduce pulmonary compliance, contributing to exertional dyspnea. The first bouts of dyspnea are usually precipitated by clinical events that increase the rate of blood flow across the mitral orifice, resulting in further elevation of the LA pressure (see below). To assess the severity of obstruction, both the transvalvular pressure gradient and the flow rate must be measured (Chap. 212). The latter depends not only on the CO but on the heart rate as well. An increase in heart rate shortens diastole proportionately more than systole and diminishes the time available for flow across the mitral valve. Therefore, at any given level of CO, tachycardia including that resulting from atrial fibrillation augments the transvalvular gradient and elevates further the LA pressure. Similar considerations apply to the tricuspid stenosis.

The LV3 diastolic pressure and ejection fraction (EF) are normal in isolated MS2. In MS and sinus rhythm, the elevated LA1 and PA4 wedge pressures exhibit a prominent atrial contraction (a wave) and a gradual pressure decline after mitral valve opening (y descent) (see Fig. 212-2). In severe MS and whenever pulmonary vascular resistance is significantly increased, the pulmonary arterial pressure (PAP) is elevated at rest and rises further during exercise, often causing secondary elevations of right ventricle (RV) end-diastolic pressure and volume.

Cardiac Output In patients with moderately severe MS2 (mitral valve orifice 1.2 cm2 to 1.7 cm2), the CO5 is normal or almost so at rest but rises subnormally during exertion. In patients with critical MS, particularly those in whom pulmonary vascular resistance is strikingly elevated, the CO is subnormal at rest and may fail to rise or may even decline during activity.

Pulmonary Hypertension The clinical and hemodynamic features of MS2 are influenced importantly by the level of the PAP6. Pulmonary hypertension results from (1) passive backward transmission of the elevated LA1 pressure; (2) pulmonary arteriolar constriction, which presumably is triggered by LA and pulmonary venous hypertension (reactive pulmonary hypertension); (3) interstitial edema in the walls of the small pulmonary vessels; and (4) organic obliterative changes in the pulmonary vascular bed. Severe pulmonary hypertension results in tricuspid regurgitation (TR) and pulmonary incompetence as well as right-sided heart failure.

SYMPTOMS

In temperate climates the latent period between the initial attack of rheumatic carditis (in the increasingly rare circumstances in which a history of one can be elicited) and the development of symptoms due to MS2 is generally about two decades; most patients begin to experience disability in the fourth decade of life. Studies carried out before the development of mitral valvotomy revealed that once a patient with MS became seriously symptomatic, the disease progressed continuously to death within 2 to 5 years. In economically deprived areas, in tropical and subtropical climates, particularly on the Indian subcontinent, in Central America, and in the Middle East, MS tends to progress more rapidly and frequently causes serious symptoms in patients less than 20 years of age. In contrast, slowly progressive MS in the elderly is being recognized with increasing frequency in the United States and Western Europe.

When valvular obstruction is mild, the physical signs of MS2 may be present without symptoms. However, even in patients whose mitral orifices are large enough to accommodate a normal blood flow with only mild elevations of LA1 pressure, marked elevations of this pressure leading to dyspnea and cough may be precipitated by severe exertion, excitement, fever, severe anemia, paroxysmal atrial fibrillation and other tachycardias, sexual intercourse, pregnancy, and thyrotoxicosis. As MS progresses, lesser stresses precipitate dyspnea, and the patient becomes limited in daily activities. The redistribution of blood from the dependent portions of the body to the lungs, which occurs when the recumbent position is assumed, leads to orthopnea and paroxysmal nocturnal dyspnea. Pulmonary edema develops when there is a sudden surge in flow across a markedly narrowed mitral orifice. When moderately severe MS has existed for several years, atrial arrhythmias occur with increasing frequency. The development of permanent AF7 often marks a turning point in the patient's course and is generally associated with acceleration of the rate at which symptoms progress.

Hemoptysis (Chap. 30) results from rupture of pulmonary-bronchial venous connections secondary to pulmonary venous hypertension. It occurs most frequently in patients who have elevated LA1 pressures without markedly elevated pulmonary vascular resistances and is almost never fatal. Recurrent pulmonary emboli (Chap. 244), sometimes with infarction, are an important cause of morbidity and mortality late in the course of MS2. Pulmonary infections, i.e., bronchitis, bronchopneumonia, and lobar pneumonia, commonly complicate untreated MS. Infective endocarditis (Chap. 109) is rare in isolated MS.

Pulmonary Changes In addition to the aforementioned changes in the pulmonary vascular bed, fibrous thickening of the walls of the alveoli and pulmonary capillaries occurs commonly in MS2. The vital capacity, total lung capacity, maximal breathing capacity, and oxygen uptake per unit of ventilation are reduced (Chap. 234), and the latter fails to rise normally during exertion. Pulmonary compliance falls further as pulmonary capillary pressure rises during exercise. In some patients, airway resistance is abnormally increased and the diffusing capacity may be reduced. These changes in the lungs are due, in part, to increased transudation of fluid from the pulmonary capillaries into the interstitial and alveolar spaces. However, the increased capacity of the pulmonary lymphatic system to drain excess fluid retards the development of alveolar edema.

Thrombi and Emboli Thrombi may form in the left atria, particularly in the enlarged atrial appendages of patients with MS2. Embolization occurs much more frequently in patients with AF8, in older patients, and in those with a reduced cardiac output (CO). However, systemic embolization may be the presenting complaint in otherwise asymptomatic patients with mild MS. Rarely, a large pedunculated or a freefloating thrombus may suddenly obstruct the stenotic mitral orifice and cause syncope, angina, and changing auscultatory signs with alterations in position.

PHYSICAL FINDINGS (SEE ALSO CHAP. 209)

Inspection and Palpation In patients with severe MS2, there may be a malar flush with pinched and blue facies. In patients with sinus rhythm and severe pulmonary hypertension or associated tricuspid stenosis (TS), the jugular venous pulse reveals prominent a waves due to vigorous right atrial systole. The systemic arterial pressure is usually normal or slightly low. An RV9 tap along the left sternal border signifies an enlarged RV. A diastolic thrill is frequently present at the cardiac apex, with the patient in the left lateral recumbent position.

Auscultation The first heart sound (S1) is generally accentuated and snapping, and slightly delayed. The pulmonary component of the second heart sound (P2) is often accentuated, and the two components of the second heart sound (S2) are closely split or fixed. A pulmonary systolic ejection click may be heard in patients with severe pulmonary hypertension. The opening snap (OS) of the mitral valve is most readily audible in expiration at, or just medial to the cardiac apex. This sound generally follows the sound of aortic valve closure (A2) by 0.05 to 0.12 s. The time interval between A2 and OS varies inversely with the severity of the MS2. The OS is followed by a low-pitched, rumbling, diastolic murmur, heard best at the apex with the patient in the left lateral recumbent position (see Fig. 209-5B). It is accentuated by mild exercise (e.g., a few rapid situps) carried out just before auscultation. In general, the duration of this murmur correlates with the severity of the stenosis. In patients with sinus rhythm, the murmur often reappears or becomes reaccentuated during atrial systole. Soft grade I or II/VI systolic murmurs are commonly heard at the apex or along the left sternal border in patients with pure MS and do not necessarily signify the presence of MR10. Hepatomegaly, ankle edema, ascites, and pleural effusion, particularly in the right pleural cavity, may occur in patients with MS and RV9 failure.

Associated Lesions With severe pulmonary hypertension, a pansystolic murmur produced by functional TR11 may be audible along the left sternal border. Characteristically, this murmur is accentuated by inspiration and diminishes during forced expiration (Carvallo's sign); it should not be confused with the apical pansystolic murmur of MR12. When the S1 and/or the OS13 are soft or absent in a patient with mitral valve disease who also has an apical systolic murmur, it is likely that significant MR and/or serious calcification of the deformed mitral valve leaflets are present. When the CO14 is markedly reduced in MS2, the typical auscultatory findings, including the diastolic rumbling murmur, may not be detectable (silent MS), but they may reappear as compensation is restored. The Graham Steell murmur of pulmonary regurgitation (PR), a high-pitched, diastolic, decrescendo blowing murmur along the left sternal border, results from dilatation of the pulmonary valve ring and occurs in patients with mitral valve disease and severe pulmonary hypertension. This murmur may be indistinguishable from the more common murmur produced by aortic regurgitation (AR).

LABORATORY EXAMINATION

EKG15 In MS2 and sinus rhythm, the P wave usually suggests LA1 enlargement (see Fig. 210-8). It may become tall and peaked in lead II and upright in lead V1 when severe pulmonary hypertension or TS16 complicates MS and right atrial (RA) enlargement occurs. The QRS complex is usually normal. However, with severe pulmonary hypertension, right axis deviation and RV9 hypertrophy are often present.

Echocardiogram (See also Chap. 211) This is the most sensitive and specific noninvasive method for diagnosing MS2. Transthoracic two-dimensional color flow Doppler echocardiographic imaging and Doppler ultrasound provide critical information, including an estimate of the transvalvular gradient and of mitral orifice size, the presence and severity of accompanying MR17, the extent of restriction of valve leaflets, their thickness, the degree of distortion of the subvalvular apparatus, and the anatomic suitability for balloon mitral valvotomy (see below). In addition, echocardiography provides an assessment of the size of the cardiac chambers, an estimation of the LV18 function, an estimation of the PAP6, and an indication of the presence and severity of associated valvular lesions. Transesophageal echocardiography provides superior images and should be employed when transthoracic imaging is inadequate for guiding therapy.

Roentgenogram The earliest changes are straightening of the left border of the cardiac silhouette, prominence of the main pulmonary arteries, dilatation of the upper lobe pulmonary veins, and backward displacement of the esophagus by an enlarged LA1. In severe MS2, however, all chambers and vessels upstream to the narrowed valve are prominent. Kerley B lines are fine, dense, opaque, horizontal lines that are most prominent in the lower and midlung fields and that result from distention of interlobular septa and lymphatics with edema when the resting mean LA pressure exceeds approximately 20 mmHg.

DIFFERENTIAL DIAGNOSIS

Like MS2, significant MR19 may also be associated with a prominent diastolic murmur at the apex, but in MR this diastolic murmur commences slightly later than in patients with MS, and there is often clear-cut evidence of LV20 enlargement. An apical pansystolic murmur of at least grade III/VI intensity as well as an S3 suggests significant associated MR. Similarly, the apical middiastolic murmur associated with AR21 (Austin Flint murmur) may be mistaken for MS. TS16, which occurs rarely in the absence of MS, may mask many of the clinical features of MS.

Atrial septal defect (Chap. 218) may be mistaken for MS2; in both conditions there is often clinical, EKG, and roentgenographic evidence of RV9 enlargement and accentuation of the pulmonary vascularity. The widely split S2 of atrial septal defect may be confused with the mitral OS22, and the diastolic flow murmur across the tricuspid valve may be mistaken for the mitral diastolic murmur. However, the absence of LA1 enlargement and of Kerley B lines and the demonstration of fixed splitting of S2 all favor atrial septal defect over MS.

Left atrial myxoma (Chap. 223) may obstruct LA1 emptying, causing dyspnea, a diastolic murmur, and hemodynamic changes resembling those of MS2. However, patients with an LA myxoma often have features suggestive of a systemic disease, such as weight loss, fever, anemia, systemic emboli, and elevated serum IgG concentrations. The auscultatory findings may change markedly with body position. The diagnosis can be established by the demonstration of a characteristic echo-producing mass in the LA with two-dimensional echocardiography.

CARDIAC CATHETERIZATION AND ANGIOCARDIOGRAPHY

Left heart catheterization is useful when there is a discrepancy between clinical and echocardiographic findings. It is helpful in assessing associated lesions such as aortic stenosis (AS) and aortic regurgitation (AR). Catheterization and coronary arteriography are not usually necessary to aid in the decision about surgery in younger patients with typical findings of severe obstruction on clinical examination and echocardiography. In males over 45 years of age, females over 55 years of age, and younger patients with coronary risk factors, especially those with positive noninvasive stress tests for myocardial ischemia, coronary angiography is usually advisable preoperatively to detect patients with critical coronary obstructions that should be bypassed at the time of operation. Catheterization and LV23 angiography are also indicated in most patients who have undergone balloon mitral valvotomy or previous mitral valve operations and who have redeveloped serious symptoms.

TREATMENT

Penicillin prophylaxis of ß-hemolytic streptococcal infections (Chap. 302) to prevent rheumatic fever and prophylaxis for infective endocarditis (Chap. 109) are important for all patients (Table 219-1). In symptomatic patients, some improvement usually occurs with restriction of sodium intake and maintenance doses of oral diuretics. Digitalis glycosides usually do not benefit patients with MS2 and sinus rhythm but are helpful in slowing the ventricular rate of patients with AF24. Beta blockers or nondihydropyridine calcium antagonists (e.g., verapamil or diltiazem) are useful in this regard. Warfarin to an INR of 2-3:1 should be administered for at least 1 year to patients with MS who have suffered systemic and/or pulmonary embolization and permanently to those with AF.

If AF25 is of relatively recent origin in a patient whose MS2 is not severe enough to warrant balloon mitral valvotomy or surgical valvotomy, reversion to sinus rhythm pharmacologically or by means of electrical countershock is indicated. Usually this reversion should be undertaken after the patient has had 3 weeks of anticoagulant treatment. Conversion to sinus rhythm is rarely helpful in patients with severe MS, particularly those in whom the LA1 is especially enlarged or in whom AF has been present for more than 1 year, since sinus rhythm is rarely sustained in such patients.

Mitral Valvotomy Unless there is a contraindication, mitral valvotomy is indicated in symptomatic patients with isolated MS2 whose effective orifice is less than approximately 1.0 cm2/m2 body surface area, or 1.7 cm2 in normal-sized adults. Mitral valvotomy can be carried out by two techniques: percutaneous balloon mitral valvotomy and surgical valvotomy. In balloon mitral valvotomy (Figs. 219-1 and 219-2), a catheter is directed into the LA1 after transseptal puncture and a single or double balloon (Inoue balloon) is directed across the valve and inflated in the valvular orifice. Ideal patients have relatively mobile, thin leaflets with no or little calcium, without extensive subvalvular thickening and with no or mild MR26. The short- and long-term results of this procedure in appropriate patients are similar to those of surgical valvotomy, but with less morbidity and a lower mortality rate. Therefore, balloon valvotomy has become the procedure of choice for such patients. Transthoracic echocardiography is helpful in identifying patients for the percutaneous procedure (Fig. 219-3).

In patients in whom percutaneous valvotomy is not possible, unsuccessful, or in those with restenosis, an "open" valvotomy using cardiopulmonary bypass is necessary. In addition to opening the valve commissures, it is important to loosen any subvalvular fusion of papillary muscles and chordae tendineae and to remove large deposits of calcium, thereby improving valvular function, as well as to remove atrial thrombi. The mortality rate is approximately 2%.

Successful valvotomy, whether balloon or surgical, usually results in striking symptomatic and hemodynamic improvement and prolongs survival. However, there is no evidence that the procedure improves the prognosis of patients with slight or no functional impairment. Therefore, unless recurrent systemic embolization or severe pulmonary hypertension has occurred, valvotomy is not recommended for patients who are entirely asymptomatic. When there is little symptomatic improvement after valvotomy, it is likely that the procedure was ineffective, that it induced MR27, or that associated valvular or myocardial disease was present. About half of all patients undergoing mitral valvotomy require reoperation by 10 years. In the pregnant patient with MS2, valvotomy should be carried out if pulmonary congestion occurs despite intensive medical treatment.

Mitral valve replacement (MVR) is necessary in patients with MS2 and significant associated MR28, those in whom the valve has been severely distorted by previous transcatheter or operative manipulation, or those in whom the surgeon does not find it possible to improve valve function significantly. Since the operative mortality rate of isolated MVR is still approximately 6% (Table 219-2), and since there are long-term complications of valve replacement, patients in whom preoperative evaluation suggests the possibility that MVR may be required should be operated on only if they have critical MS, i.e., an orifice =1 cm2 area and are in New York Heart Association class III, i.e., symptomatic with ordinary activity despite optimal medical therapy. The overall 10-year survival of surgical survivors is approximately 70%. Long-term prognosis is worse in older patients and those with marked disability and striking depression of the cardiac index preoperatively


	2. mitral regurgitation

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MITRAL REGURGITATION

ETIOLOGY

Chronic rheumatic heart disease is the cause of severe MR29 in only about one-third of cases and occurs more frequently in males. The rheumatic process produces rigidity, deformity, and retraction of the valve cusps and commissural fusion, as well as shortening, contraction, and fusion of the chordae tendineae. MR may occur as a congenital anomaly (Chap. 218), most commonly as a defect of the endocardial cushions (atrioventricular cushion defects). MR is frequently secondary to ischemia. Thus, it may occur as a consequence of ventricular remodeling or with fibrosis of a papillary muscle in patients with healed myocardial infarction. It may develop acutely in patients with acute infarction involving the base of a papillary muscle. Transient MR also may occur during periods of ischemia involving a papillary muscle or the adjacent myocardium and may accompany bouts of angina pectoris. MR may occur with marked LV30 enlargement of any cause in which dilatation of the mitral annulus and lateral displacement of the papillary muscles interfere with coaptation of the valve leaflets, most commonly ischemia. In hypertrophic cardiomyopathy, the anterior leaflet of the mitral valve is displaced anteriorly during systole, causing MR (Chap. 221). Calcification of the mitral annulus of unknown cause, presumably degenerative, which occurs most commonly in elderly women, also can be responsible for significant MR. Acute MR may occur secondary to infective endocarditis involving the valve leaflets or chordae tendineae, or as a consequence of trauma. Mitral valve prolapse (MVP), an important cause of MR, is considered in the next section.

Irrespective of cause, severe MR31 is often progressive, since enlargement of the LA1 places tension on the posterior mitral leaflet, pulling it away from the mitral orifice and thereby aggravating the valvular dysfunction. Similarly, LV32 dilatation increases the regurgitation, which in turn enlarges the LA and LV further, causing chordal rupture and resulting in a vicious circle; hence the aphorism, "mitral regurgitation begets mitral regurgitation."

PATHOPHYSIOLOGY

The resistance to LV33 emptying is reduced in patients with MR34. As a consequence, the LV is decompressed into the LA1 during ejection, and with the reduction in LV size during systole, there is a rapid decline in LV tension. The initial compensation to acute MR is more complete LV emptying. However, LV volume increases progressively as the severity of the regurgitation increases and as LV function deteriorates. This increase in LV volume is often accompanied by a reduced forward CO35. The regurgitant volume varies directly with the LV systolic pressure and the size of the regurgitant orifice; as mentioned above, the latter, in turn, is influenced profoundly by the extent of LV dilatation. Since ejection fraction (EF) rises in severe MR in the presence of normal LV function, even a modest reduction in this parameter (60%) reflects significant dysfunction.

The v wave in the LA1 pressure pulse is usually prominent (see Fig. 212-3). During early diastole, as the distended LA empties, there is a particularly rapid y descent (as long as there is no associated MS2). In chronic MR36, there is often an increase in LV37 compliance, so that LV volume rises with little elevation in LV diastolic pressure. The effective (forward) CO38 is usually reduced in seriously symptomatic patients. A brief, early diastolic atrioventricular pressure gradient (often accompanying a murmur) may occur in patients with pure MR as a result of the very rapid flow of blood across a normal-sized mitral orifice.

The prompt appearance of contrast material in the LA1 after its injection into the LV39 signifies the presence of MR40. The regurgitant volume can be measured by determining the difference between the total LV stroke volume, estimated angiocardiographically, and the effective forward stroke volume determined by the Fick method (Chap. 212). In severe cases, as much as 50% of the total LV stroke volume regurgitates with each beat. Qualitative, but clinically useful, estimates of the severity of regurgitation may be made by observation on cineangiograms of the degree of LA opacification after the injection of contrast material into the LV. Color flow Doppler imaging is most commonly used for this purpose (see below).

Left ventricular contractility becomes reduced, sometimes irreversibly, with longstanding MR41. The compliance, i.e., the pressure-volume relationship of the LA1 and pulmonary venous bed affects the clinical picture. Patients with acute MR usually have normal or reduced LA compliance, with little enlargement of the LA, but marked elevation of the LA pressure, particularly of the v wave. Severe pulmonary congestion and pulmonary edema are common in this group. Patients with a marked increase in LA compliance are at the opposite end of the spectrum, having longstanding, severe MR, marked enlargement of the LA, and normal or only slightly elevated LA and PA4 pressures. These patients usually complain of severe fatigue and exhaustion secondary to a low CO42, while symptoms resulting from pulmonary congestion are less prominent; AF43 is almost invariably present. Most common are patients whose clinical and hemodynamic features are intermediate between those in the two aforementioned groups.

SYMPTOMS

Fatigue, exertional dyspnea, and orthopnea are the most prominent complaints in patients with chronic, severe MR44. Systemic embolism occurs less frequently than in MS2. Right-sided heart failure, with painful hepatic congestion, ankle edema, distended neck veins, ascites, and TR11, occur in patients with MR who have associated pulmonary vascular disease and marked pulmonary hypertension. In patients with acute, severe MR, LV45 failure with acute pulmonary edema is common.

PHYSICAL FINDINGS

The arterial pressure is usually normal, and in patients with severe MR46 the arterial pulse may show a sharp upstroke. The jugular venous pulse shows abnormally prominent a waves in patients with sinus rhythm and marked pulmonary hypertension and prominent v waves in those with accompanying severe TR11. A systolic thrill is often palpable at the cardiac apex, the LV47 is hyperdynamic with a brisk systolic impulse and a palpable rapid-filling wave, and the apex beat is often displaced laterally. An RV9 tap and the shock of pulmonary valve closure may be palpable in patients with marked pulmonary hypertension.

Auscultation The S1 is generally absent, soft, or buried in the systolic murmur. In patients with severe MR48, the aortic valve may close prematurely, resulting in wide splitting of the S2. An OS49 indicates associated MS2 but does not exclude predominant regurgitation. A low-pitched S3 occurring 0.12 to 0.17 s after the aortic valve closure sound, i.e., at the completion of the rapid-filling phase of the LV50, is believed to be caused by the sudden tensing of the papillary muscles, chordae tendineae, and valve leaflets and is an important auscultatory feature of severe MR. The S3 may be followed by a short, rumbling, diastolic murmur, even in the absence of MS. A fourth heart sound is often audible in patients with acute, severe MR of recent onset who are in sinus rhythm. A presystolic murmur is not ordinarily heard with isolated MR but is present in patients with sinus rhythm and associated MS.

A systolic murmur of at least grade III/VI intensity, is the most characteristic auscultatory finding in severe MR51. It is usually holosystolic (see Figs. 209-4 and 209-5A), but it may be decrescendo and cease in late systole in patients with acute, severe MR. In MR due to papillary muscle dysfunction or MVP52, the systolic murmur commences in midsystole (see below). The systolic murmur is usually most prominent at the apex and radiates to the axilla. However, in patients with ruptured chordae tendineae or primary involvement of the posterior mitral leaflet, the regurgitant jet strikes the LA1 wall adjacent to the aortic root. In this situation, the systolic murmur is transmitted to the base of the heart and therefore may be confused with the murmur of AS53. In patients with ruptured chordae tendineae the systolic murmur may have a cooing or "sea gull" quality, while a flail leaflet may cause a murmur with a musical quality. The systolic murmur of MR is intensified by isometric strain but is reduced during the Valsalva maneuver.

LABORATORY EXAMINATION

Electrocardiogram In patients with sinus rhythm there is evidence of LA1 enlargement, but RA54 enlargement also may be present when pulmonary hypertension is severe. Chronic, severe MR55 is generally associated with AF56. In many patients there is no clear-cut electrocardiographic evidence of enlargement of either ventricle. In others, the signs of LV57 hypertrophy are present.

Echocardiogram Color flow Doppler imaging is the most accurate noninvasive technique for the detection and estimation of MR58. Two-dimensional echocardiography is useful for assessing the cause of MR and for estimating LV59 function from end-systolic and end-diastolic volumes and EF60. The LA1 is usually enlarged and/or exhibits increased pulsation while the LV may be hyperdynamic. Findings that help to determine the etiology of MR, such as mitral annular calcification and LV dyskinesis in ischemic MR, can often be identified by two-dimensional echocardiography. With ruptured chordae tendineae or a flail leaflet, coarse, erratic motion of the involved leaflets may be noted. Vegetations associated with infective endocarditis, incomplete coaptation of the anterior and posterior mitral leaflets, and annular calcification, as well as MR secondary to LV dilatation, aneurysm, or dyskinesis may be recognized. Transesophageal imaging provides greater detail than transthoracic imaging (see Fig. 211-3). The echocardiogram in patients with MVP61 is described in the next section.

Roentgenogram The LA1 and LV62 are the dominant chambers; late in the course of the disease, the former may be massively enlarged and forms the right border of the cardiac silhouette. Pulmonary venous congestion, interstitial edema, and Kerley B lines are sometimes noted. Marked calcification of the mitral leaflets occurs commonly in patients with longstanding combined MR63 and MS2. Calcification of the mitral annulus may be visualized.

TREATMENT

MEDICAL (TABLE 219-1) The nonsurgical management of patients with severe MR64 begins with restricting those physical activities that regularly produce dyspnea and excessive fatigue, reducing sodium intake, and enhancing sodium excretion with the appropriate use of diuretics (Chap. 216). Vasodilators and digitalis glycosides increase the forward output of the failing LV65. Intravenous nitroprusside or nitroglycerin reduce afterload and thereby the volume of regurgitant flow and are useful in stabilizing patients with acute and/or severe MR. Angiotensin-converting enzyme (ACE) inhibitors are useful in the treatment of chronic MR. The same considerations as in patients with MS2 apply to the reversion of AF66 to sinus rhythm. In the late stages of heart failure anticoagulants and leg binders are used to diminish the likelihood of venous thrombi and pulmonary emboli. Endocarditis prophylaxis is important. In patients with severe MR secondary to dilated cardiomyopathy, intensive medial therapy can reduce the severity of MR.

SURGICAL In the selection of patients with severe MR67 for surgical treatment, the chronic, often slowly progressive nature of the condition must be balanced against the immediate and long-term risks associated with the operation. Patients with MR who are asymptomatic or who are limited only during strenuous exertion and whose LV functions are normal are not considered to be candidates for surgical treatment, since their condition may remain stable for years. By contrast, unless there are contraindications, surgical treatment should be offered to patients with severe MR whose limitations do not allow fulltime employment or the performance of normal household activities despite optimal medical management. Surgical treatment of severe MR should be considered even in asymptomatic patients or those with mild symptoms when LV68 dysfunction is progressive, with LV EF69 declining below 60% and/or end-systolic cavity dimension on echocardiography rising above 45 mm. In patients with impaired LV function, the risk of surgery rises, the recovery of LV performance is incomplete, and the long-term survival is reduced (Fig. 219-4). However, conservative management has little to offer these patients, so operative treatment may be indicated and occasionally, the clinical and hemodynamic improvement that follows surgical treatment of patients with advanced disease is dramatic. However, unless chordal continuity can be preserved, operation is contraindicated in patients whose LV ejection fraction has declined to below 30%. Though most patients who survive surgery appear to be greatly improved, some degree of myocardial dysfunction often persists.

When surgical treatment is contemplated, left-sided heart catheterization and angiocardiography may be helpful in confirming the presence of severe MR70 in patients in whom there is a discrepancy between the clinical picture and the echocardiographic findings; these procedures may also aid in detecting and assessing the severity of associated valve lesions. Importantly, coronary arteriography identifies patients who require concomitant coronary revascularization.

Surgical treatment of MR71, especially that caused by valves that are markedly deformed, with shrunken, calcified leaflets secondary to rheumatic fever, requires MVR72 with a prosthesis. However, in an increasing number of patients, particularly those with severe annular dilatation, flail leaflets, MVP73, ruptured chordae, or infective endocarditis, reconstruction of the mitral valve apparatus (mitral valvuloplasty) and/or mitral annuloplasty with an annuloplasty ring may be successful. Valve reconstruction should be carried out whenever feasible since the operative risk is about half (~3%) of that associated with MVR (Table 219-1). Also, reconstruction spares the patient the long-term adverse consequences of valve replacement, i.e., thromboembolic and hemorrhagic complications in the case of mechanical prostheses and late valve failure necessitating repeat valve replacement in the case of bioprostheses. In addition, by preserving the integrity of the papillary muscles, subvalvular apparatus and chordae tendinae, mitral repair and valvuloplasty maintains LV74 function. In asymptomatic patients with preserved left ventricular function, surgical treatment can be considered as long as mitral repair seems feasible and pulmonary hypertension or recent atrial fibrillation are present.

MITRAL VALVE PROLAPSE

MVP75, also variously termed the systolic click-murmur syndrome, Barlow's syndrome, floppy-valve syndrome, and billowing mitral leaflet syndrome, is a relatively common, but highly variable clinical syndrome resulting from diverse pathogenic mechanisms of the mitral valve apparatus. Among these are excessive or redundant mitral leaflet tissue, which is commonly associated with myxomatous degeneration and greatly increased concentrations of acid mucopolysaccharide. MVP is a frequent finding in patients with heritable disorders of connective tissue, including the Marfan syndrome (Chap. 342), osteogenesis imperfecta, and the Ehler-Danlos syndrome. In most patients with MVP, however, myxomatous degeneration is confined to the mitral (or less commonly the tricuspid or aortic) valves without other clinical or pathologic manifestations of disease. The posterior leaflet is usually more affected than the anterior, and the mitral valve annulus is often greatly dilated. In many patients, elongated redundant chordae tendineae cause or contribute to the regurgitation.

In most patients with MVP76, the cause is unknown, but in some it appears to be a genetically determined collagen tissue disorder. A reduction in the production of type III collagen has been incriminated, and electron microscopy has revealed fragmentation of collagen fibrils. MVP may be associated with thoracic skeletal deformities similar to but not as severe as those in the Marfan syndrome, including a high-arched palate and alterations of the chest and thoracic spine, including the so-called straight back syndrome. MVP also may occur as a sequel of acute rheumatic fever, in ischemic heart disease, and in cardiomyopathies, as well as in 20% of patients with ostium secundum atrial septal defect.

MVP77 may lead to excessive stress on the papillary muscles, which in turn leads to dysfunction and ischemia of the papillary muscles and the subjacent ventricular myocardium. Rupture of chordae tendineae and progressive annular dilatation and calcification also contribute to valvular regurgitation, which then places more stress on the diseased mitral valve apparatus, thereby creating a vicious circle. The electrocardiographic changes (see below) and ventricular arrhythmias appear to result from regional ventricular dysfunction related to increased stress placed on the papillary muscles.

CLINICAL FEATURES

MVP78 is more common in females. It affects individuals in a wide age range but most commonly those between the ages of 14 and 30 years. The clinical course is often benign. MVP may also be observed in older (50 years) patients, often males, and in them MR79 is more often severe and requires surgical treatment. There is an increased familial incidence for some patients, suggesting an autosomal dominant form of inheritance. MVP encompasses a broad spectrum of severities, ranging from only a systolic click and murmur and mild prolapse of the posterior leaflet of the mitral valve to severe MR due to chordal rupture and massive prolapse of both leaflets. In many patients, this condition progresses over years or decades.

Most patients are asymptomatic and remain so for their entire lives. However, MVP80 is now the most common cause of isolated severe MR81 requiring surgical treatment in North America. Arrhythmias, most commonly ventricular premature contractions and paroxysmal supraventricular and ventricular tachycardia, have been reported and may cause palpitations, light-headedness, and syncope. Sudden death is a very rare complication. Many patients have chest pain that is difficult to evaluate. It is often substernal, prolonged, poorly related to exertion, and rarely resembles angina pectoris. Transient cerebral ischemic attacks secondary to emboli from the mitral valve due to endothelial disruption have been reported. Infective endocarditis may occur in patients with MR associated with MVP.

Auscultation The most important finding is the mid- or late (nonejection) systolic click, which occurs 0.14 s or more after the S1 and is thought to be generated by the sudden tensing of slack, elongated chordae tendineae or by the prolapsing mitral leaflet when it reaches its maximum excursion. Systolic clicks may be multiple and may be followed by a high-pitched, late systolic crescendo-decrescendo murmur, which occasionally is "whooping" or "honking," and is heard best at the apex. The click and murmur occur earlier with standing, during the strain of the Valsalva maneuver, and with any intervention that decreases LV82 volume, exaggerating the propensity of mitral leaflet prolapse. Conversely, squatting and isometric exercise, which increase LV volume, diminish MVP83, and the click-murmur complex is delayed and may even disappear. Some patients have a midsystolic click without the murmur; others have the murmur without a click. Still others have both sounds at different times.

LABORATORY EXAMINATION

The ECG84 most commonly is normal but may show biphasic or inverted T waves in leads II, III, and aVF, and occasionally supraventricular or ventricular premature contractions. Two-dimensional echocardiography is particularly effective in identifying the abnormal position and prolapse of the mitral valve leaflets. A useful echocardiographic definition of MVP85 is systolic displacement (in the parasternal view) of the mitral valve leaflets by at least 2 mm into the LA1 superior to the plane of the mitral annulus. Thickening of the mitral valve leaflets identifies a subgroup of patients at higher risk of infective endocarditis and the development of severe MR86. Prolapse of the tricuspid and/or aortic valve may be found. Color-imaging and Doppler studies are helpful in revealing and evaluating accompanying MR. Angiocardiography generally shows prolapse of the posterior and sometimes of both mitral valve leaflets.

TREATMENT

The management of patients with MVP87 consists of the asymptomatic patient without severe MR88 or arrhythmias and the prevention of infective endocarditis with antibiotic prophylaxis in patients with a systolic murmur and/or thickening of mitral valve leaflets on endocardiography. Beta blockers sometimes relieve chest pain. If symptomatic tachyarrhythmias have occurred, antiarrhythmic agents as dictated by electrophysiologic studies should be administered. If the patient is symptomatic from severe MR, mitral valve repair (or rarely, replacement) is indicated. Antiplatelet aggregation agents such as aspirin should be given to patients with transient ischemic attacks, and if these are not effective, anticoagulants should be used.


	3. aortic stenosis

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AORTIC STENOSIS

AS89 occurs in about one-fourth of all patients with chronic valvular heart disease; approximately 80% of adult patients with symptomatic valvular AS are male.

ETIOLOGY

AS90 in adults may be due to degenerative calcification of the aortic cusps. It may be congenital in origin or it may be secondary to rheumatic inflammation. Age-related degenerative calcific AS (also known as senile or sclerocalcific AS) is now the most common cause of AS in adults in North America and Western Europe. About 30% of persons 65 years exhibit aortic valve sclerosis, many of whom have a systolic murmur of AS but without obstruction, while an additional 2% exhibit frank stenosis. On histologic examination these valves frequently exhibit inflammatory changes similar to those seen in atherosclerotic vessels. Interestingly, risk factors for atherosclerosis, such as age, male sex, smoking, diabetes mellitus, hypertension, increased LDL, reduced HDL cholesterol, and elevated C-reactive protein are all risk factors for aortic valve calcification.

The congenitally affected valve may be stenotic at birth (Chap. 218) and may become progressively more fibrotic, calcified, and stenotic. In other cases the valve may be congenitally deformed, usually bicuspid, without serious narrowing of the aortic orifice during childhood; its abnormal architecture makes its leaflets susceptible to otherwise ordinary hemodynamic stresses, which ultimately lead to valvular thickening, calcification, increased rigidity, and narrowing of the aortic orifice.

Rheumatic endocarditis of the aortic leaflets produces commissural fusion, sometimes resulting in a bicuspid valve. This condition in turn, makes the leaflets more susceptible to trauma and ultimately leads to fibrosis, calcification, and further narrowing. By the time the obstruction to LV91 outflow causes serious clinical disability, the valve is usually a rigid calcified mass, and careful examination may make it difficult or even impossible to determine the etiology of the underlying process. Rheumatic AS92 is almost always associated with involvement of the mitral valve and by associated severe AR93.

OTHER FORMS OF OBSTRUCTION TO LEFT VENTRICULAR OUTFLOW

Besides valvular AS94, three other lesions may be responsible for obstruction to LV95 outflow.

1. Hypertrophic cardiomyopathy (Chap. 221). This condition is characterized by marked hypertrophy of the LV96 and involves in particular the interventricular septum; it may cause subaortic obstruction.

2. Discrete congenital subvalvular AS97 (Chap. 218). This congenital anomaly is produced by either a membranous diaphragm or a fibrous ridge just below the aortic valve.

3. Supravalvular AS98 (Chap. 218). This uncommon congenital anomaly is produced by narrowing of the ascending aorta or by a fibrous diaphragm with a small opening just above the aortic valve.

PATHOPHYSIOLOGY

The obstruction to LV99 outflow produces a systolic pressure gradient between the LV and aorta. When severe obstruction is suddenly produced experimentally, the LV responds by dilatation and reduction of stroke volume. However, in patients the obstruction may be present at birth and/or increase gradually over the course of many years, and LV output is maintained by the presence of concentric LV hypertrophy. This serves as a useful compensatory mechanism because it reduces toward normal the systolic stress developed by the myocardium. A large transaortic valvular pressure gradient may exist for many years without a reduction of CO100 or LV dilatation; ultimately, however, these changes occur.

A peak systolic pressure gradient 50 mmHg in the face of a normal cardiac output or an effective aortic orifice less than approximately 1.0 cm2 or 0.6 cm2/m2 body surface area, i.e., less than approximately one-third of the normal orifice, is generally considered to represent severe obstruction to LV101 outflow. The elevated LV end-diastolic pressure observed in many patients with severe AS102 signifies the presence of LV dilatation and/or diminished compliance of the hypertrophied LV wall. A large a wave in the LA1 pressure pulse is usually present. Although the CO103 at rest is within normal limits in most patients with severe AS, it usually fails to rise normally during exercise. Loss of an appropriately timed, vigorous atrial contraction, as occurs in AF104 or atrioventricular dissociation, may cause a rapid progression of symptoms. Late in the course the CO and LV-aortic pressure gradient decline, and the mean LA, PA4, and RV9 pressures rise.

The hypertrophied LV105 muscle mass elevates myocardial oxygen requirements. In addition, even in the absence of obstructive coronary artery disease, there may be interference with coronary blood flow. This is because the pressure compressing the coronary arteries exceeds the coronary perfusion pressure, often causing ischemia, especially in the subendocardium, and during tachycardia, both in the presence and in the absence of coronary arterial narrowing.

SYMPTOMS

AS106 is rarely of clinical importance until the valve orifice has narrowed to approximately 0.5 cm2/m2 body surface area in adults. Even severe AS may exist for many years without producing any symptoms because of the ability of the hypertrophied LV107 to generate the elevated intraventricular pressures required for a normal stroke volume.

Most patients with pure or predominant AS108 have gradually increasing obstruction for years but do not become symptomatic until the sixth to eighth decades. Exertional dyspnea, angina pectoris, and syncope are the three cardinal symptoms. Often there is a history of insidious progression of fatigue and dyspnea associated with gradual curtailment of activities. Dyspnea results primarily from elevation of the pulmonary capillary pressure caused by elevations of LV109 diastolic pressures secondary to reduced compliance. Angina pectoris usually develops somewhat later and reflects an imbalance between the augmented myocardial oxygen requirements and reduced oxygen availability; the former results from the increased myocardial mass and intraventricular pressure, while the latter may result from accompanying coronary artery disease, which is not uncommon in patients with AS, as well as from compression of the coronary vessels by the hypertrophied myocardium. Therefore, angina may occur in severe AS even without obstructive epicardial coronary artery disease. Exertional syncope may result from a decline in arterial pressure caused by vasodilatation in the exercising muscles and inadequate vasoconstriction in nonexercising muscles in the face of a fixed CO110, or from a sudden fall in CO produced by an arrhythmia.

Since the CO111 at rest is usually well maintained until late in the course, marked fatigability, weakness, peripheral cyanosis, and other clinical manifestations of a low CO are usually not prominent until this stage is reached. Orthopnea, paroxysmal nocturnal dyspnea, and pulmonary edema, i.e., symptoms of LV112 failure, also occur only in the advanced stages of the disease. Severe pulmonary hypertension leading to RV9 failure and systemic venous hypertension, hepatomegaly, AF113, and TR11 are usually late findings in patients with isolated, severe AS114.

When AS115 and MS2 coexist, the reduction of cardiac output induced by MS lowers the pressure gradient across the aortic valve and thereby masks many of the clinical findings produced by AS. Left heart catheterization is helpful in defining the relative importance of each valvular abnormality.

PHYSICAL FINDINGS

The rhythm is generally regular until very late in the course; at other times, AF116 should suggest the possibility of associated mitral valve disease. The systemic arterial pressure is usually within normal limits. In the late stages, however, when stroke volume declines, the systolic pressure may fall and the pulse pressure narrow. Systemic hypertension is unusual in patients with severe AS117. The peripheral arterial pulse, as palpated in the carotid or brachial arteries, rises slowly to a delayed sustained peak (pulsus parvus et tardus) (see Fig. 209-2). In the elderly, the stiffening of the arterial wall may mask this important physical sign. A palpable double systolic arterial pulse, the so-called bisferiens pulse, excludes pure or predominant AS and signifies dominant AR118. In the late stages of AS, when the pulse pressure is reduced, the pulse amplitude may be so small that the anacrotic nature of the pulse and the delay in its upstroke may become difficult to appreciate. In many patients the a wave in the jugular venous pulse is accentuated. This results from the diminished distensibility of the RV9 cavity caused by the bulging, hypertrophied intraventricular septum.

The LV119 impulse is usually active and displaced laterally, reflecting the presence of LV hypertrophy. A double apical impulse may be recognized, particularly with the patient in the left lateral recumbent position. A systolic thrill is generally present at the base of the heart, in the jugular notch, and along the carotid arteries. In patients who do not have marked pulmonary emphysema, a thick chest wall, thoracic deformity, or heart failure, the absence of a systolic thrill suggests that the AS120 is relatively mild.

Auscultation An early systolic ejection sound, actually the OS121 of the aortic valve, is frequently audible in children and adolescents with congenital noncalcific valvular AS122. This sound usually disappears when the valve becomes calcified and rigid. As AS increases in severity, LV123 systole may become prolonged so that the aortic valve closure sound no longer precedes the pulmonic valve closure sound, and the two components may become synchronous, or aortic valve closure may even follow pulmonic valve closure, causing paradoxic splitting of the S2 (Chap. 209). The sound of aortic valve closure can be heard most frequently in patients with AS who have pliable valves, and calcification diminishes the intensity of this sound. Frequently, an S4 is audible at the apex and reflects the presence of LV hypertrophy and an elevated LV end-diastolic pressure; an S3 generally occurs when the LV dilates.

The murmur of AS124 is characteristically an ejection (mid) systolic murmur that commences shortly after the S1, increases in intensity to reach a peak toward the middle of ejection, and ends just before aortic valve closure (see Figs. 209-4 and 209-5A). It is characteristically low-pitched, rough and rasping in character, and loudest at the base of the heart, most commonly in the second right intercostal space. It is transmitted upward along the carotid arteries. Occasionally, it is transmitted downward and to the apex where it may be confused with the systolic murmur of MR125. In almost all patients with severe obstruction, the murmur is at least grade III/VI. In patients with mild degrees of obstruction or in those with severe stenosis with heart failure in whom the stroke volume and therefore the transvalvular flow rate are reduced, the murmur may be relatively soft and brief.

LABORATORY EXAMINATION

Electrocardiogram In most patients with severe AS126 there is LV127 hypertrophy (see Fig. 210-9). In advanced cases, ST-segment depression and T-wave inversion (LV "strain") in standard leads I and aVL and in the left precordial leads are evident. However, there is no close correlation between the ECG128 and the hemodynamic severity of obstruction, and the absence of ECG signs of LV hypertrophy does not exclude severe obstruction.

The key findings are LV129 hypertrophy and, in patients with valvular calcification (i.e., most adult patients with symptomatic AS130), multiple, bright, thick, echoes from within the aortic root. Eccentricity of the aortic valve cusps is characteristic of congenitally bicuspid valves. Transesophageal imaging usually displays the obstructed orifice extremely well. The transaortic valvular gradient can be estimated by Doppler echocardiography. LV dilatation and reduced systolic shortening reflect impairment of LV function. Echocardiography is also useful for identifying valvular abnormalities such as MS2 and AR131, which sometimes accompany AS, and for differentiating valvular AS from obstructive hypertrophic cardiomyopathy.

Roentgenogram The chest roentgenogram may show no or little overall cardiac enlargement for many years, since the development of concentric LV132 hypertrophy is the initial response to obstruction to LV outflow. Hypertrophy without dilatation may produce some rounding of the cardiac apex in the frontal projection and slight backward displacement in the lateral view; critical AS133 is often associated with poststenotic dilatation of the ascending aorta (Fig. 211-5). Aortic calcification is usually readily apparent on fluoroscopic examination or by echocardiography; the absence of valvular calcification in an adult suggests that severe valvular AS is not present. In later stages of the disease as the LV dilates, there is increasing roentgenographic evidence of LV enlargement; pulmonary congestion; and enlargement of the LA1, PA4, and right side of the heart.

Catheterization Catheterization of the left side of the heart and coronary arteriography should generally be carried out in patients suspected of having severe AS134 who are being considered for operative treatment. These investigations are especially indicated in the following:

1. Patients with clinical signs of AS and symptoms of myocardial ischemia, in whom associated coronary artery disease is suspected. An effort should be made to determine whether AS or coronary atherosclerosis is primarily responsible for the symptoms. Coronary arteriography should be carried out to identify patients who require coronary bypass grafting at the time of aortic valve surgery.

2. Patients with multivalvular disease, in whom the role played by each valvular deformity should be defined to aid in the planning of definitive operative treatment.

3. Young, asymptomatic patients with noncalcific congenital AS, to define with precision the severity of obstruction to LV135 outflow, since operation [which does not usually require aortic valve replacement (AVR)] or balloon valvotomy may be indicated if severe AS is present, even in the absence of symptoms. Balloon valvotomy may follow left heart catheterization immediately.

4. Patients in whom it is suspected that the obstruction to LV136 outflow may not be at the aortic valve but rather in the sub- or supravalvular regions.

NATURAL HISTORY

Death in patients with severe AS137 occurs most commonly in the seventh and eighth decades. Based on data obtained at postmortem examination in patients before surgical treatment became widely available, the average time to death after the onset of various symptoms was as follows: angina pectoris, 3 years; syncope, 3 years; dyspnea, 2 years; and congestive heart failure, 1.5 to 2 years. Moreover, in 80% of patients who died with AS, symptoms had existed for 4 years. Congestive heart failure was considered to be the cause of death in one-half to two-thirds of patients. Among adults dying with valvular AS, sudden death, which presumably resulted from an arrhythmia, occurred in 10 to 20% and at an average age of 60 years. However, most sudden deaths occur in patients who had previously been symptomatic; thus sudden death is very uncommon (3 per 1000 patient years) in asymptomatic patients with severe AS. Obstructive calcific AS is a progressive disease, with an annual reduction in valve area of approximately 0.1 mm2/year.

TREATMENT

Medical Treatment (Fig. 219-5, Table 219-1) In patients with severe AS138 (0.5 cm2/m2), strenuous physical activity should be avoided, even in the asymptomatic stage. Sodium restriction, the cautious administration of diuretics and digitalis glycosides are indicated in the treatment of congestive heart failure, but care must be taken to avoid volume depletion since this may cause a marked reduction of CO139. Nitroglycerin is helpful in relieving angina pectoris. Retrospective studies have shown that patients with degenerative calcific AS who receive HMG-CoA reductase inhibitors ("statins") exhibit slower progression of leaflet calcification and aortic valve area reduction than those who do not. Treatment with these relatively safe agents should be considered while the results of clinical trials are awaited.

Surgical Treatment The most critical decision in the management of AS140 concerns the advisability of surgical treatment which, in most adults with calcific AS and severe obstruction consists of AVR141. However, these patients should be followed carefully for the development of symptoms and by serial echocardiograms for evidence of deteriorating LV142 function. Operation is generally indicated in patients with severe AS (valve area 1.0 cm2 or 0.6 cm2/m2 body surface area) who are symptomatic, those who exhibit LV dysfunction, as well as those with an expanding poststenotic aortic root, even if they are asymptomatic. In patients without heart failure, the operative risk of AVR is approximately 4% (Table 219-2). In most instances, it is prudent to postpone operation in patients with severe calcific AS who are asymptomatic and who exhibit normal LV143 function, i.e., EF144 50%, since they may continue to do well for many years. The risk of surgical mortality exceeds that of sudden death in asymptomatic patients. However, AVR can be carried out in asymptomatic patients with severe stenosis who undergo coronary artery bypass grafting.

Operation should, if possible, be carried out before frank LV145 failure develops; at this late stage, the aortic valve pressure gradient declines as the stroke volume and ejection fraction decline. In such patients, the operative risk is high (15 to 20%), and evidence of myocardial disease may persist even when the operation is technically successful. Furthermore, long-term postoperative survival also correlates inversely with preoperative LV dysfunction. Nonetheless, in view of the even worse prognosis of such patients when they are treated medically, there is usually little choice but to advise surgical treatment, especially in patients in whom contractile reserve can be demonstrated by dobutamine echocardiography. In patients in whom severe AS146 and coronary artery disease coexist, relief of the AS and revascularization of the myocardium by means of aortocoronary bypass grafting may result in striking clinical and hemodynamic improvement.

Because many patients with calcific AS147 are elderly, particular attention must be directed to the adequacy of hepatic, renal, and pulmonary function before AVR148 is recommended. The mortality rate depends to a substantial extent on the patient's preoperative clinical and hemodynamic state. The 10-year survival rate of patients with AVR is approximately 60%. Approximately 30% of bioprosthetic valves evidence primary valve failure in 10 years, requiring rereplacement, and an approximately equal percentage of patients with mechanical prostheses develop significant hemorrhagic complications as a consequence of treatment with anticoagulants.

Percutaneous Balloon Aortic Valvuloplasty This procedure is preferable to operation in children and young adults with congenital, noncalcific AS149. It is not commonly used in adults with severe calcific AS because of a high restenosis rate, but has on occasion been used successfully in patients as a "bridge to operation" in patients with severe LV150 dysfunction who are too ill to tolerate surgery.


	4. artic regurgitatio

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AORTIC REGURGITATION

ETIOLOGY

AR may be caused by primary valve disease or by primary aortic root disease.

Primary Valve Disease Approximately three-fourths of patients with pure or predominant valvular AR are males; females predominate among patients with primary valvular AR who have associated mitral valve disease. In approximately two-thirds of patients with AR the disease is rheumatic in origin, resulting in thickening, deformity, and shortening of the individual aortic valve cusps, changes that prevent their proper opening during systole and closure during diastole. A rheumatic origin is less common in patients with isolated AR. Patients with congenital membranous subaortic stenosis often develop thickening of the aortic valve leaflets, which makes the valves particularly susceptible to endocarditis. AR also may occur in patients with rheumatoid spondylitis and in patients with congenital bicuspid aortic valves. Prolapse of an aortic cusp, resulting in progressive chronic AR, occurs in approximately 15% of patients with ventricular septal defect (Chap. 218). Congenital fenestrations of the aortic valve occasionally produce mild AR.

Acute AR may result from infective endocarditis, which can develop on a valve previously affected by rheumatic disease, a congenitally deformed valve, or, rarely, on a normal aortic valve, and perforate or erode one or more of the leaflets. Although traumatic rupture of the aortic valve is an uncommon cause of acute AR, it does represent the most frequent serious lesion in patients surviving nonpenetrating cardiac injuries. The coexistence of hemodynamically significant AS with AR usually excludes all the rarer forms of AR because it occurs almost exclusively in patients with rheumatic or congenital AR. In patients with AR due to primary valvular disease, dilatation of the aortic annulus may occur secondarily and intensify the regurgitation.

Primary Aortic Root Disease AR both acute and chronic, also may be due entirely to marked aortic dilatation, i.e., aortic root disease, without primary involvement of the valve leaflets; widening of the aortic annulus and separation of the aortic leaflets are responsible for the AR (Chap. 231). Cystic medial necrosis of the ascending aorta, which may or may not be associated with other manifestations of the Marfan syndrome, idiopathic dilatation of the aorta, osteogenesis imperfecta, and severe hypertension all may widen the aortic annulus and lead to progressive AR. Occasionally, AR is caused by retrograde dissection of the aorta involving the aortic annulus. Syphilis and rheumatoid ankylosing spondylitis may be associated with cellular infiltration and scarring of the media of the thoracic aorta, leading to aortic dilatation, aneurysm formation, and severe regurgitation. In syphilis of the aorta, now a very rare condition (Chap. 153), the involvement of the intima may narrow the coronary ostia, which in turn may be responsible for myocardial ischemia.

PATHOPHYSIOLOGY

The total stroke volume ejected by the LV (i.e., the sum of the effective forward stroke volume and the volume of blood that regurgitates back into the LV) is increased in patients with AR. In patients with wide-open (free) AR, the volume of regurgitant flow may equal the effective forward stroke volume. In contrast to MR, in which a fraction of the LV stroke volume is delivered into the low-pressure LA1, in AR the entire LV stroke volume is ejected into a high-pressure zone, the aorta. An increase in the LV end-diastolic volume (increased preload) constitutes the major hemodynamic compensation for AR. The dilatation and eccentric hypertrophy of the LV allows this chamber to eject a larger stroke volume without requiring any increase in the relative shortening of each myofibril. Therefore, severe AR may occur with a normal effective forward stroke volume and a normal left ventricular EF [total (forward plus regurgitant) stroke volume/end-diastolic volume], together with an elevated LV end-diastolic pressure and volume. However, through the operation of Laplace's law (which holds that myocardial wall tension is the product of intracavitary pressure and LV radius), LV dilatation increases the LV systolic tension required to develop any given level of systolic pressure. Ultimately, these adaptive measures fail. As LV function deteriorates, the end-diastolic volume rises further and the forward stroke volume and EF decline. Deterioration of LV function often precedes the development of symptoms. Considerable thickening of the LV wall also occurs with chronic AR, and at autopsy the hearts of these patients may be among the largest encountered, sometimes weighing 1000 g.

The reverse pressure gradient from aorta to LV, which drives the AR flow, falls progressively during diastole (see Fig. 212-4), accounting for the decrescendo nature of the diastolic murmur. Equilibration between aortic and LV pressures may occur toward the end of diastole in patients with severe AR, particularly when the heart rate is slow, and the LV end-diastolic pressure may be elevated, occasionally to extremely high levels (40 mmHg). Rarely, in acute, severe AR, the LV pressure exceeds the LA1 pressure toward the end of diastole, and this reversed pressure gradient closes the mitral valve prematurely or causes diastolic MR.

In patients with severe AR, the effective forward CO usually is normal or only slightly reduced at rest, but often it fails to rise normally during exertion. Early signs of LV dysfunction include reduction in the EF, determined by echocardiography or radionuclide angiography. In advanced stages there may be considerable elevation of the LA1, PA4 wedge, PA, and RV9 pressures and lowering of the forward CO at rest.

Myocardial ischemia may occur in patients with AR because myocardial oxygen requirements are elevated by both LV dilatation and elevated LV systolic tension. However, a large fraction of coronary blood flow occurs during diastole, when arterial pressure is subnormal, thereby reducing coronary perfusion pressure. This combination of increased oxygen demand and reduced supply may cause myocardial ischemia, particularly of the subendocardium, even in the absence of concomitant coronary artery disease.

HISTORY

A family history may frequently be elicited from patients with AR associated with the Marfan syndrome. A history compatible with infective endocarditis may sometimes be elicited from patients with rheumatic or congenital involvement of the aortic valve, and the infection often precipitates or seriously aggravates preexisting symptoms. Ankylosing spondylitis is usually self evident.

In patients with acute, severe AR, as may occur in infective endocarditis or trauma, the LV cannot dilate sufficiently to maintain stroke volume, and LV diastolic pressure rises rapidly with associated elevations of LA1 and PA4 wedge pressures. Pulmonary edema and/or cardiogenic shock may develop rapidly.

Chronic, severe AR may have a long latent period, and patients may remain relatively asymptomatic for as long as 10 to 15 years. However, uncomfortable awareness of the heartbeat, especially on lying down, may be an early complaint. Sinus tachycardia during exertion or with emotion, or premature ventricular contractions may produce particularly uncomfortable palpitations, as well as head pounding. These complaints may persist for many years before the development of exertional dyspnea, usually the first symptom of diminished cardiac reserve. The dyspnea is followed by orthopnea, paroxysmal nocturnal dyspnea, and excessive diaphoresis. Anginal chest pain occurs frequently in patients with severe AR, even in younger patients, and it is not necessary to invoke the presence of coronary artery disease to explain this symptom in patients with severe AR. Anginal pain may develop at rest as well as during exertion. Nocturnal angina may be a particularly troublesome symptom, and it may be accompanied by marked diaphoresis. The anginal episodes can be prolonged and often do not respond satisfactorily to sublingual nitroglycerin. Systemic fluid accumulation, including congestive hepatomegaly and ankle edema, may develop late in the course of the disease.

PHYSICAL FINDINGS

In severe AR, the jarring of the entire body and the bobbing motion of the head with each systole can be appreciated, and the abrupt distention and collapse of the larger arteries are easily visible. The examination should be directed toward the detection of conditions predisposing to AR, such as the Marfan syndrome, rheumatoid ankylosing spondylitis, and ventricular septal defect.

Arterial Pulse A rapidly rising "water-hammer" pulse, which collapses suddenly as arterial pressure falls rapidly during late systole and diastole (Corrigan's pulse), and capillary pulsations, an alternate flushing and paling of the skin at the root of the nail while pressure is applied to the tip of the nail (Quincke's pulse), are characteristic of free AR. A booming, "pistol-shot" sound can be heard over the femoral arteries (Traube's sign), and a to-and-fro murmur (Duroziez's sign) is audible if the femoral artery is lightly compressed with a stethoscope.

The arterial pulse pressure is widened, with an elevation of the systolic pressure, sometimes to as high as 300 mmHg, and a depression of the diastolic pressure. The measurement of arterial diastolic pressure with a sphygmomanometer may be complicated by the fact that systolic sounds are frequently heard with the cuff completely deflated. However, the level of cuff pressure at the time of muffling of the Korotkoff sounds (Phase IV) generally corresponds fairly closely to the true intraarterial diastolic pressure. The severity of AR does not always correlate directly with the arterial pulse pressure, and severe regurgitation may exist in patients with arterial pressures in the range of 140/60 mmHg. As the disease progresses and the LV end-diastolic pressure rises markedly, the arterial diastolic pressure may actually rise also, since the aortic diastolic pressure cannot fall below the LV end-diastolic pressure. For the same reason, severe, acute AR may also be accompanied by only light widening of the pulse pressure.

Palpation The LV impulse is heaving and displaced laterally and inferiorly. The systolic expansion and diastolic retraction of the apex are prominent and contrast with the sustained systolic thrust characteristic of severe AS. A diastolic thrill is often palpable along the left sternal border, and a prominent systolic thrill may be palpable in the jugular notch and transmitted upward along the carotid arteries. This systolic thrill and the accompanying murmur are due to the markedly increased blood flow across the aortic orifice and do not necessarily signify the coexistence of AS. In many patients with pure AR or with combined AS and AR, the carotid arterial pulse is bisferiens, i.e., with two systolic waves separated by a trough.

Auscultation In patients with severe AR, the aortic valve closure sound (A2) is usually absent. An S3 and systolic ejection sound are frequently audible, and occasionally, an S4 also may be heard. The murmur of chronic AR is typically a high-pitched, blowing, decrescendo diastolic murmur, heard best in the third intercostal space along the left sternal border (see Fig. 209-5B). In patients with mild AR, this murmur is brief, but as the severity increases, generally becomes louder and longer, indeed holodiastolic. When the murmur is soft, it can be heard best with the diaphragm of the stethoscope and with the patient sitting up, leaning forward, and with the breath held in forced expiration. In patients in whom the AR is caused by primary valvular disease, the diastolic murmur is usually louder along the left than the right sternal border. However, when the murmur is heard best along the right sternal border, it suggests that the AR is caused by aneurysmal dilatation of the aortic root. "Cooing" or musical diastolic murmurs suggest eversion of an aortic cusp vibrating in the regurgitant stream.

A midsystolic ejection murmur is frequently audible in AR. It is generally heard best at the base of the heart and is transmitted along the carotid vessels. This murmur may be quite loud without signifying aortic obstruction; it is often higher pitched, shorter, and less rasping in quality than the ejection systolic murmur heard in patients with predominant AS. A third murmur frequently heard in patients with severe AR is the Austin Flint murmur, a soft, low-pitched, rumbling middiastolic bruit. It is probably produced by the diastolic displacement of the anterior leaflet of the mitral valve by the AR stream but does not appear to be associated with hemodynamically significant mitral obstruction and, in contrast to the diastolic murmur of MS2, it is not accompanied by an OS or loud S1. The auscultatory features of AR are intensified by isometric exercise such as strenuous handgrip, which augments systemic resistance, and reduced by inhalation of amyl nitrite.

In severe, acute AR, the elevation of LV end-diastolic pressure may lead to early closure of the mitral valve, an associated middiastolic sound, a soft or absent S1, a pulse pressure that is not particularly wide, and a soft, short diastolic murmur of AR.

LABORATORY EXAMINATION

EKG In patients with severe, chronic AR, the EKG signs of LV hypertrophy become manifest (Chap. 210). In addition, these patients frequently exhibit ST-segment depression and T-wave inversion in leads I, aVL, V5, and V6 ("LV strain"). Left axis deviation and/or QRS prolongation denote diffuse myocardial disease, generally associated with patchy fibrosis, and usually signify a poor prognosis.

Echocardiogram The extent and velocity of wall motion are normal or even supernormal, until myocardial contractility declines. A rapid, high-frequency fluttering of the anterior mitral leaflet produced by the impact of the regurgitant jet is a characteristic finding. The echocardiogram is also useful in determining the cause of AR, by detecting dilatation of the aortic annulus (Fig. 219-6). Thickening and failure of coaptation of the leaflets also may be noted. Color flow Doppler echocardiographic imaging is very sensitive in the detection of AR, and Doppler echocardiography is helpful in assessing its severity. Serial two-dimensional echocardiography is valuable in assessing LV performance and in detecting progressive myocardial dysfunction.

Roentgenogram In severe chronic AR, the apex is displaced downward and to the left in the frontal projection, and frequently the cardiac shadow extends below the left diaphragm. LV enlargement also may be apparent in the left anterior oblique and lateral projections, in which the LV is displaced posteriorly and encroaches on the spine. In patients in whom primary valvular disease is responsible for the AR, the ascending aorta and aortic knob may be moderately dilated. When AR is caused by primary disease of the aortic wall, aneurysmal dilatation of the aorta may be noted, and the aorta may fill the retrosternal space in the lateral view.

Cardiac Catheterization and Angiography In addition to providing an accurate confirmation of the magnitude of regurgitation and the status of LV function, the condition of the coronary arterial bed should ordinarily be evaluated preoperatively.

TREATMENT

Medical Treatment (Table 219-1) Although operation constitutes the definitive treatment of AR and should be carried out before the development of heart failure, the latter usually responds briefly to treatment with digitalis glycosides, salt restriction, diuretics, and vasodilators, especially ACE inhibitors. Digitalis also may be indicated in patients with severe regurgitation and dilated left ventricles without frank LV failure. Cardiac arrhythmias and infections are poorly tolerated in patients with severe AR and must be treated promptly and vigorously. Although nitroglycerin and long-acting nitrates are not as helpful in relieving anginal pain as they are in patients with ischemic heart disease, they are worth a trial. Long-acting nifedipine has been found to delay the need for operation. Patients with syphilitic aortitis should receive a full course of penicillin therapy (Chap. 153).

Surgical Treatment In deciding on the advisability and proper timing of surgical treatment, two points should be kept in mind: (1) patients with chronic AR usually do not become symptomatic until after the development of myocardial dysfunction, and (2) when delayed too long, surgical treatment often does not restore normal LV function. Therefore, in patients with severe AR, careful clinical follow-up and noninvasive testing with echocardiography at approximately 6-month intervals are necessary if operation is to be undertaken at the optimal time, i.e., after the onset of LV dysfunction but prior to the development of severe symptoms. Operation can be deferred as long as the patient both remains asymptomatic and retains normal LV function. In general, operation should be carried out even in asymptomatic patients with progressive LV dysfunction and a left ventricular ejection fraction (LVEF)55% or a LV end-systolic volume 55 mL/m2. These parameters have been referred to as the "55/55 rule."

AVR with a suitable mechanical or tissue prosthesis is generally necessary in patients with rheumatic AR and in many patients with other forms of regurgitation. Rarely, when a leaflet has been perforated during infective endocarditis or torn from its attachments to the aortic annulus by thoracic trauma, surgical repair may be possible. When AR is due to aneurysmal dilatation of the annulus and ascending aorta rather than to primary valvular involvement, it may be possible to reduce the regurgitation by narrowing the annulus or by excising a portion of the aortic root without replacing the valve. More frequently, however, regurgitation can be eliminated only by replacing the aortic valve, excising the dilated or aneurysmal ascending aorta responsible for the regurgitation, and replacing it with a graft. This formidable procedure entails a higher risk than isolated AVR.

As in patients with other valvular abnormalities, both the operative risk and the late mortality are largely dependent on the stage of the disease and on myocardial function at the time of operation. The overall operative mortality for isolated AVR is 4.3% (Table 219-2). However, patients with marked cardiac enlargement and prolonged LV dysfunction experience an operative mortality rate of approximately 10% and a late mortality rate of approximately 5% per year due to LV failure despite a technically satisfactory operation. Nonetheless, because of the very poor prognosis with medical management, even patients with LV failure should be considered for operation.

Patients with acute, severe AR require prompt surgical treatment, which may be lifesaving.


	5. tricuspid valve

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TRICUSPID STENOSIS

TS16, a relatively uncommon valvular lesion in North America and Western Europe, is more common in tropical and subtropical climates, especially in southern Asia and in Latin America. It is generally rheumatic in origin and is more common in females than in males. It does not occur as an isolated lesion and is usually associated with MS2. Hemodynamically significant TS occurs in 5 to 10% of patients with severe MS; rheumatic TS is commonly associated with some degree of TR11.

PATHOPHYSIOLOGY

A diastolic pressure gradient between the RA203 and RV9 can be recorded with a double-lumen cardiac catheter. It is augmented when the transvalvular blood flow increases during inspiration and declines during expiration. A mean diastolic pressure gradient of 4 mmHg is usually sufficient to elevate the mean RA pressure to levels that result in systemic venous congestion. Unless sodium intake has been restricted and diuretics administered, this venous congestion is associated with ascites and edema, sometimes severe. In patients with sinus rhythm, the RA a wave may be extremely tall and may even approach the level of the RV systolic pressure. The CO204 at rest is usually depressed and it fails to rise during exercise. The low CO is responsible for the normal or only slightly elevated LA1, PA4, and RV systolic pressures despite the presence of MS2. Thus, the presence of TS16 can mask the hemodynamic and clinical features of the MS which usually accompanies it.

SYMPTOMS

Since the development of MS2 generally precedes that of TS16, many patients initially have symptoms of pulmonary congestion. Amelioration of these symptoms should raise the possibility that TS may be developing. Characteristically, patients complain of relatively little dyspnea for the degree of hepatomegaly, ascites, and edema that they have. However, fatigue secondary to a low CO205 and discomfort due to refractory edema, ascites, and marked hepatomegaly are common in patients with TS and/or TR11. In some patients, TS may be suspected for the first time when symptoms of RV9 failure persist after an adequate mitral valvotomy.

PHYSICAL FINDINGS

Since TS16 usually occurs in the presence of other obvious valvular disease, the diagnosis may be missed unless it is specifically searched for. Severe TS is associated with marked hepatic congestion, often resulting in cirrhosis, jaundice, serious malnutrition, anasarca, and ascites. Congestive hepatomegaly and, in cases of severe tricuspid valve disease, splenomegaly are present. The jugular veins are distended, and in patients with sinus rhythm there may be giant a waves. The v waves are less conspicuous, and since tricuspid obstruction impedes RA206 emptying during diastole, there is a slow y descent. In patients with sinus rhythm there may be prominent presystolic pulsations of the enlarged liver as well.

On auscultation, the pulmonic valve closure sound is not accentuated, and occasionally, an OS207 of the tricuspid valve may be heard approximately 0.06 s after pulmonic valve closure. The diastolic murmur of TS16 has many of the qualities of the diastolic murmur of MS2, and since TS almost always occurs in the presence of MS, the less common valvular lesion may be missed. However, the tricuspid murmur is generally heard best along the left lower sternal margin and over the xiphoid process and is most prominent during presystole in patients with sinus rhythm. The diastolic murmur is reduced in amplitude as the stethoscope is inched laterally, only to intensify or reappear as the mitral murmur at the apex. The murmur of TS is augmented during inspiration, and it is reduced during expiration and particularly during the strain of Valsalva maneuver, when tricuspid blood flow is reduced.

LABORATORY EXAMINATION

The ECG208 features of RA209 enlargement (Chap. 210) include tall, peaked P waves in lead II, as well as prominent, upright P waves in lead V1. The absence of ECG evidence of right ventricular hypertrophy (RVH) in a patient with right-sided heart failure who is believed to have MS2 should suggest associated tricuspid valve disease. The chest roentgenogram in patients with combined TS16 and MS shows particular prominence of the RA and superior vena cava without much enlargement of the PA4 and with less evidence of pulmonary vascular congestion than occurs in patients with isolated MS. On echocardiographic examination, the tricuspid valve is usually thickened; the transvalvular gradient can be estimated by Doppler echocardiography.

TREATMENT

Patients with TS16 generally exhibit marked systemic venous congestion; intensive salt restriction and diuretic therapy are required during the preoperative period. Such a preparatory period may diminish hepatic congestion and thereby improve hepatic function sufficiently so that the risks of operation are diminished. Surgical relief of the TS should be carried out, preferably at the time of surgical mitral valvotomy or MVR210, in patients with moderate or severe TS who have mean diastolic pressure gradients exceeding approximately 4 mmHg and tricuspid orifices less than 1.5 to 2.0 cm2. TS is almost always accompanied by significant TR11. Open-heart repair may permit substantial improvement of tricuspid valve function. If this cannot be accomplished, the tricuspid valve may have to be replaced with a prosthesis, preferably a large bioprosthetic valve.

TRICUSPID REGURGITATION

Most commonly, TR11 is functional and secondary to marked dilatation of the tricuspid annulus. Functional TR may complicate RV9 enlargement of any cause, including inferior wall infarcts that involve the RV. It is commonly seen in the late stages of heart failure due to rheumatic or congenital heart disease with severe pulmonary hypertension, as well as in ischemic heart disease, cardiomyopathy, and cor pulmonale. It is in part reversible if pulmonary hypertension is relieved. Rheumatic fever may produce organic TR, often associated with TS16. Infarction of RV papillary muscles, tricuspid valve prolapse, carcinoid heart disease, endomyocardial fibrosis, infective endocarditis, and trauma all may produce TR. Less commonly, TR results from congenitally deformed tricuspid valves, and it occurs with defects of the atrioventricular canal as well as with Ebstein's malformation of the tricuspid valve (Chap. 218).

As is the case for TS16, the clinical features of TR11 result primarily from systemic venous congestion and reduction of CO211. With the onset of TR in patients with pulmonary hypertension, symptoms of pulmonary congestion diminish, but the clinical manifestations of right-sided heart failure become intensified. The neck veins are distended with prominent v waves; and marked hepatomegaly, ascites, pleural effusions, edema, systolic pulsations of the liver, and a positive hepatojugular reflux are common. A prominent RV9 pulsation along the left parasternal region and a blowing holosystolic murmur along the lower left sternal margin, which may be intensified during inspiration and reduced during expiration or the strain of the Valsalva maneuver, are characteristic findings; AF212 is usually present.

The ECG213 usually shows changes characteristic of the lesion responsible for the enlargement of the RV9 that leads to TR11, e.g., inferior wall myocardial infarction or severe RVH214. Echocardiography may be helpful by demonstrating RV dilatation and prolapsing or flail tricuspid leaflets; the diagnosis of TR can be made by color flow Doppler echocardiography, and the severity estimated by Doppler examination. The latter is also useful in estimating PA4 pressure. Roentgenographic examination usually reveals enlargement of both the RA215 and RV.

In patients with severe TR11, the CO216 is usually markedly reduced, and the RA217 pressure pulse may exhibit no x descent during early systole but a prominent c-v wave with a rapid y descent. The mean RA and the RV9 end-diastolic pressures are often elevated.

TREATMENT

Isolated TR11, in the absence of pulmonary hypertension, such as that occurring as a consequence of infective endocarditis or trauma, is usually well tolerated and does not require operation. Indeed, even total excision of an infected tricuspid valve may be well tolerated for several years if the PA4 pressure is normal. Treatment of the underlying cause of heart failure usually reduces the severity of functional TR by reducing the size of the tricuspid annulus. In patients with mitral valve disease and TR secondary to pulmonary hypertension and massive RV9 enlargement, effective surgical correction of the mitral valvular abnormality results in lowering of the PA pressures and gradual reduction or disappearance of the TR without direct treatment of the tricuspid valve. However, recovery may be much more rapid in patients with severe secondary TR if, at the time of mitral valve surgery, tricuspid annuloplasty (generally with the insertion of a plastic ring), open tricuspid valve repair, or, in the rare instance of severe organic tricuspid valve disease, tricuspid valve replacement is performed. Surgical treatment of the TR also should be carried out in patients with severe regurgitation secondary to deformity of the tricuspid valve due to rheumatic fever, particularly those without severe pulmonary hypertension.


	6. pulmonary valv

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PULMONIC VALVE DISEASE

The pulmonic valve is affected by rheumatic fever far less frequently than are the other valves, and it is uncommonly the seat of infective endocarditis. The most common acquired abnormality affecting the pulmonic valve is regurgitation secondary to dilatation of the pulmonic valve ring as a consequence of severe pulmonary hypertension. This produces the Graham Steell murmur, a high-pitched, decrescendo, diastolic blowing murmur along the left sternal border, which is difficult to differentiate from the far more common murmur produced by AR218. It is usually of little hemodynamic significance; indeed, surgical removal or destruction of the pulmonic valve by infective endocarditis does not produce heart failure unless serious pulmonary hypertension is also present. The carcinoid syndrome may cause pulmonic stenosis and/or regurgitation. Congenital pulmonic stenosis is discussed in Chap. 218.

VALVE REPLACEMENT

The results of replacement of any valve are dependent primarily on (1) the patient's myocardial function and general medical condition at the time of operation; (2) the technical abilities of the operative team and the quality of the postoperative care; and (3) the durability, hemodynamic characteristics, and thrombogenicity of the prosthesis. Increased operative mortality is associated with advanced age, comorbidity (e.g., pulmonary or renal disease, the need for nonvalvular cardiovascular surgery, diabetes mellitus) as well as with higher levels of preoperative functional disability and pulmonary hypertension. Late complications of valve replacement include paravalvular leakage, thromboemboli, bleeding due to anticoagulants, mechanical dysfunction of the prosthesis, and infective endocarditis.

The considerations involved in the choice between a bioprosthetic (tissue) and artificial mechanical valve are similar in the mitral and aortic sites and in the treatment of stenotic, regurgitant, or mixed lesions. All patients who have undergone replacement of any valve with a mechanical prosthesis are at risk of thromboembolic complications and must be maintained permanently on anticoagulants, a treatment that imposes a hazard of hemorrhage. The primary advantage of bioprostheses over mechanical prostheses is the virtual absence of thromboembolic complications 3 months after implantation, and except for patients with chronic AF219, few such instances have been associated with their use. The major disadvantage of bioprosthetic valves is their mechanical deterioration, the incidence of which is inversely proportional to the patient's age. This results in the need to replace the prosthesis in 30% of patients by 10 years and in 50% by 15 years. Because this complication is age-related, bioprostheses are ordinarily not used in patients under 65 years but are particularly useful in the elderly (70 years), in whom there is more concern about chronic anticoagulation than about long-term (20 years) valve durability. Patients between 65 and 70 years should be evaluated on a case-by-case basis as to the use of a bioprosthetic or mechanical valve. Bioprosthetic valves are also indicated in women who expect to become pregnant, as well as others in whom anticoagulation may be contraindicated. Alternative bioprostheses are xenografts [i.e., porcine aortic valves; cryopreserved, mounted bovine pericardium; homograft (allograft) aortic valves obtained from cadavers as well as pulmonary autografts transplanted into the aortic position.]

In patients without contraindications to anticoagulants, particularly those under 65 years, a mechanical prosthesis may be preferable. Many surgeons now select the St. Jude prosthesis, a double-disk tilting prosthesis, for replacement of both aortic and mitral valves because of favorable hemodynamic characteristics and possible association with lower thrombogenicity.


End file.
